1. Field of the Invention
The present invention relates to imaging sensors and, more specifically, to a method and system for calibrating such imaging sensors.
2. Background Art
Imaging sensors are used to detect illumination or radiation from scenes using focal plane arrays (“FPAs”), also referred to as FPA detectors. Focal plane arrays are composed of light sensitive elements, referred to herein as pixels. When illumination is incident upon such a light sensitive element, it generates an intensity measurement indicating the strength or level of illumination applied to the element.
In an example application, FPA detectors are designed as area spectrometers having a large number of light sensitive elements for receiving illumination. Once illumination is incident upon such an FPA detector, each of the light sensitive elements produces an intensity measurement. Because each light sensitive element tends to have a different response to illumination as compared to each of the other light sensitive elements, a non-uniform intensity response is generated across the FPA detector. This non-uniform intensity response reduces the utility of images produced by the FPA detector. Alternatively, the non-uniform intensity response tends to reduce the utility of light sensor by masking the features of the scene.
Therefore, it is desirable that a uniform intensity response be generated by the FPA detector so that a clearer image can be generated. Conventionally, there have been several methods to correct the intensity response across the FPA detector to make it more uniform. However, such methods produced inadequate results because of an operational variations in the response of the FPA detector to different illuminations. Furthermore, conventional methods generated short-term drift as well as long-term aging in the response of the FPA detector. Therefore, there is a need for an improved method of generating a uniform response of the FPA detector to illumination in operational sensors.